This invention pertains generally to flight vehicles and particularly to airborne flight vehicles wherein four independent control surfaces are used to control flight of the airborne flight vehicle.
In a flight vehicle, control surfaces are used to provide pitch, yaw and roll control of the flight vehicle. For example, control surfaces such as control fins are used to control flight of a missile and a torpedo. Additionally, control surfaces such as jet exhaust ports are used to control flight of a torpedo in water and a vehicle in space.
As it is known, in various controlled flight vehicles, including a controlled missile, commands to control the control surfaces are produced by a guidance system in the missile and provided to an autopilot to control the flight of the missile. In one conventional missile guidance technique, a pitch command, a yaw command and a roll command are provided by the guidance system to the autopilot so that the autopilot may provide control signals to fin control circuitry to command the control fins for control of the missile.
Typically in a missile, two control fins are used for pitch control, two orthogonally positioned control fins are used for yaw control and all four control fins are used for roll control. In an environment wherein the missile must maneuver, one of the control fins is deflected to a larger angle than the other control fins. Typically, the autopilot, when providing the control signals to the fin control circuitry, will apportion the roll requirement to each of the control fins and then apportion the pitch and yaw requirement. In an environment wherein a maneuver requires a control fin deflection greater than that capable by the control fin, then typically the roll apportionment is given priority by the autopilot and the pitch and yaw requirement is reduced to a degree that is allowed by maximum deflection of the control fin. In such a condition, the control fins cannot respond as necessary and the missile cannot maneuver as required.